I think we can all agree that watching a “nice ride” in any discipline is a pleasure that invokes happiness and inspiration in all horse people. The rider’s correct position and body awareness plays a vital role in creating those rounds that look so effortless but in reality took many hours in the saddle to perfect.
Does your instructor sound like a broken record telling you lesson after lesson the same thing for example “close your fingers” or “look up”? Often habits are difficult to change no matter how hard we try but take heart in the fact that any habit can be changed with persistence and repetition. As the expression goes “perfect practice makes perfect”.
A program of strengthening and fitness out of the saddle can definitely help with body awareness. I would also suggest creating a mental checklist of the things you want to change and a cue to remind yourself to review it. For example make it a habit every time you do a transition or ride by the gate to tell yourself “elbows in” or “reins shorter”. With time and effort you will find that as you ride by the gate your checklist is already done and you can add the accomplishment of changing a bad habit to your list of achievements.
I encourage you to tackle one thing about your position you want to change by creating your own mental checklist and finding a cue to remind yourself to use it and let me know how it works for you.